Application of structured illumination to gas phase thermometry using thermographic phosphor particles: a study for averaged imaging

Research output: Contribution to journalArticle

Abstract

Structured laser illumination planar imaging (SLIPI) is combined with gas phase thermometry measurements using thermographic phosphor (TGP) particles. The technique is applied to a heated jet surrounded by a coflow which is operated at ambient temperature. The respective air flows are seeded with a powder of BaMgAl10O17:Eu2+ (BAM) which is used as temperature-sensitive gas phase tracer. Upon pulsed excitation in the ultraviolet spectral range, the temperature is extracted based on the two-color ratio method combined with SLIPI. The main advantage of applying the SLIPI approach to phosphor thermometry is the reduction of particle-to-particle multiple light scattering and diffuse wall reflections, yielding a more robust calibration procedure as well as improving the measurement accuracy, precision, and sensitivity. For demonstration, this paper focuses on sample-averaged measurements of temperature fields in a jet-in-coflow configuration. Using the conventional approach, which in contrast to SLIPI is based on imaging with an unmodulated laser light sheet, we show that for the present setup typically ~40% of the recorded signal is affected by the contribution of multiply scattered photons. At locations close to walls even up to 75% of the apparent signal is due to diffuse reflection and wall luminescence of BAM sticking at the surface. Those contributions lead to erroneous temperature fields. Using SLIPI, an unbiased two-color ratio field is recovered allowing for two-dimensional mean temperature reconstructions which exhibit a more realistic physical behavior. This is in contrast to results deduced by the conventional approach. Furthermore, using the SLIPI approach it is shown that the temperature sensitivity is enhanced by a factor of up to ~2 at ~270 °C. Finally, an outlook towards instantaneous SLIPI phosphorescence thermometry is provided.

Details

Authors
  • Florian Zentgraf
  • Michael Stephan
  • Edouard Berrocal
  • Barbara Albert
  • Benjamin Böhm
  • Andreas Dreizler
Organisations
External organisations
  • Technical University of Darmstadt
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics
  • Energy Engineering
Original languageEnglish
Article number82
JournalExperiments in Fluids
Volume58
Issue number7
Publication statusPublished - 2017 Jul 1
Publication categoryResearch
Peer-reviewedYes